Method for producing a transport/drive belt

ABSTRACT

A method for forming a longitudinal edge region of a transport/drive belt having at least two layers of a thermoplastic material and at least one layer of a woven fabric web includes positioning a mat at one longitudinal edge of the transport/drive belt. The method further includes transferring heat and pressure to the transport/drive belt so as to melt and merge at least a region of the at least two layers of thermoplastic material without adding any additional material, solidifying the at least two layers of thermoplastic material, and removing the mat.

The invention relates to a method for producing a transport/drive beltcomprising at least one layer of a thermoplastic material and at leastone layer of a woven fabric web.

Such belts which are generally planar have many uses as conveyor beltsor also as drive belts. In this instance, in particular the edges at thelongitudinal edges of the extended belts are subject to a highmechanical load and stress during use, so that the peripheral edges ofthe belt are often unprotected against environmental influences withprolonged use and can be penetrated by particles of dirt and germs. Thisis unacceptable in all commercial fields involving the production,processing and sale of foodstuffs, in particular with regard to goodhygiene practice and the HACCP concept (Hazard Analysis and CriticalControl Point).

DE 1 237 768 discloses a production method for conveyor belts, wherein acarrier strip with a material strip adhesively-bonded thereto is movedtowards and placed around an edge of a belt. Subsequently, the elastomerof the material strip is melted and formed by pressing heated plates onthe upper and lower side of the conveyor belt. The basic notion of thisinvention involves fitting additional elastomer material at the edge ofthe conveyor belt and bonding it into a unit with the elastomer materialof the conveyor belt under the action of temperature and pressure.

DE 1 289 300 discloses a conveyor belt which has a core with tensilestrength comprising a plurality of woven fabric inserts which areconnected by means of connecting layers of thermoplastic material. Thewarp threads of the woven fabric insert comprise, in the edge zones ofthe fabric, a thermoplastic material which melts under the action oftemperature and pressure and bonds to form a unit with the thermoplasticmaterial of the connection layers. However, these thermoplastic warpthreads have a low level of tensile strength with the result that theyare undesirable in practice. Such warp threads are therefore often usedonly with specific spacing, so that the edge in this region can beseparated which, however, makes flexible production completelyimpossible.

GB 1,030,354 and U.S. Pat. No. 5,244,083 describe methods whereinconveyor belts comprise a plurality of layers, which have differentwidths in the peripheral regions. The widest peripheral layer is foldedaround the other material layers. However, with belts which are producedin this manner, it is also possible for the multilayer structure tobecome delaminated or frayed.

On this basis, an object of the invention is to make it possible toproduce a transport/drive belt with a sealed and durable edge in asimple and cost-effective manner.

This object is achieved according to the invention with a methodaccording to the features of claim 1.

The subsidiary claims relate to the additional configuration of thedevice.

With a production method of the type described in the introduction,there is provision according to the invention for a mat to be positionedat least at one longitudinal edge of the transport/drive belt in orderto transfer heat and/or pressure to the transport/drive belt so thatexclusively the thermoplastic material of the transport/drive belt ismelted and formed at least in regions without any additional materialand subsequently, after the thermoplastic material has solidified again,the mat is removed from the longitudinal edge of the transport/drivebelt.

The central notion of the present invention is that the thermoplasticmaterial particularly of the plurality of belt layers which is alreadyavailable, for example, PVC, PU, PE, PA, PP or polyolefins, is formedinto a uniform and sealed belt edge. Removal of material or fitting ofadditional material is therefore not required. With the transport/drivebelt produced in this manner, the resolidified material forms a unit atthe edge so that the plurality of layers cannot become separated orloose.

In order not to impair the tensile strength which is determinedsubstantially by the material properties of the woven fabric insert,there is provision according to the invention for the meltingtemperature of the material of the woven fabric web to be higher thanthe melting temperature of the thermoplastic material.

In a production method according to the invention, the melting andforming of the thermoplastic material is preferably carried out in atemperature range of between 120° C. and 200° C., more preferably in atemperature range of between 160° C. and 180° C.

In order to reliably prevent adhesion of the thermoplastic material inthe molten and/or resolidified state, it is possible to provide, betweenthe transport/drive belt and the mat, whilst the method according to theinvention is being carried out, a separation medium, for example, aseparation paper or a separation film.

So that the formed edge surface has a desired surface structure, forexample, with a rough/smooth or matt/gloss property, the separationmedium can be provided with a surface structure which is impressedduring melting and forming of the surface of the thermoplastic material.

Advantageously, in a method according to the invention, the mat isconstructed as a glass fibre mat.

The mat can readily be removed from the formed belt together with theseparation medium if the mat has a woven fabric which is coated withanti-adhesive agent.

Various configurations of the invention are permitted. The basic notionof the method according to the invention is explained in greater detailbelow by way of example with reference to an embodiment and the appendedFigures, in which:

FIG. 1 is a schematic cross-section of a transport/drive belt whichcomprises a plurality of layers, prior to the melting and formingoperation;

FIG. 2 illustrates the transport/drive belt with a longitudinal edgeformed according to the invention.

The illustration of FIG. 1 shows a transport/drive belt 1 which has aplurality of layers of thermoplastic material 2, which are arranged in asubstantially parallel manner one above the other. Between each twolayers of thermoplastic material 2, for example, polyvinyl chloride,polyurethane, polyethylene, polyamide, polypropylene and/or apolyolefin, a woven fabric web 3 is inserted as an intermediate layer.In order to simplify the illustration, the individual threads, that isto say, the weft or warp threads of the woven fabric web 3, are drawn ina non-separated state. It is important that they do not protrude beyondthe thermoplastic material 2.

Around one of the two edges of the transport/drive belt 1, the left edgein the plane of the drawing, a sack or pocket-like mat 4 is movedtowards and placed around the belt edge. Between the mat 4 and thethermoplastic material 2 of the transport/drive belt 1, there isarranged a separation paper 5 which is also guided around the entireedge from an upper side to the lower side.

For the actual forming operation, two heating plates 6 are placed at theupper side and the lower side of the arrangement comprising thetransport/drive belt 1, separation paper 5 and mat 4. Using the heatingplates 6, a temperature and/or pressure action is transmitted to thearrangement described above. The temperature is selected in such amanner that, although the thermoplastic material 2 in the edge regionmelts, the woven fabric webs 3 whose material has a higher meltingtemperature do not.

After the thermoplastic material 2 has melted, it is formed by thepressure applied so that the molten masses of the plurality of layers atleast partially merge. The melting of the thermoplastic material 2 iscarried out in particular in a temperature range of between 160° C. and180° C. In place of the illustrated heating plates 6, it is alsopossible to position a high-grade steel film as a heating means aroundthe arrangement.

FIG. 2 illustrates the transport/drive belt 1 of FIG. 1 after theforming operation with resolidified thermoplastic material 2. In FIG. 2,it can clearly be seen that the forming operation carried out inaccordance with the invention has no significant influence on the wovenfabric webs 3. However, it can also clearly be seen at the processededge of the transport/drive belt 1 that the thermoplastic material 2which was originally in several layers forms a unit with a rounded edgeafter the forming operation.

For clarity, in FIGS. 1 and 2, only the longitudinal edge illustrated atthe left-hand side in each case is processed and formed. Thelongitudinal edge drawn at the right-hand side in each case remainsunchanged and the separated layers of the various materials can clearlybe seen. For the use of the transport/drive belt, however, there ispreferably provision for both longitudinal edges to be correspondinglyformed and sealed.

1-8. (canceled)
 9. A method for forming a longitudinal edge region of atransport/drive belt having at least two layers of a thermoplasticmaterial and at least one layer of a woven fabric web, the methodcomprising: positioning a mat at one longitudinal edge of thetransport/drive belt; transferring heat and pressure to thetransport/drive belt so as to melt and merge at least a region of the atleast two layers of thermoplastic material without adding any additionalmaterial; solidifying the at least two layers of thermoplastic material;and removing the mat.
 10. The method as recited in claim 9, wherein amelting temperature of the woven fabric web is higher than a meltingtemperature of the thermoplastic material.
 11. The method as recited inclaim 9, wherein the melting is performed at a temperature range ofbetween 120° C. and 200° C.
 12. The method as recited in claim 9,wherein the melting is performed at a temperature range of between 160°C. and 180° C.
 13. The method as recited in claim 9, further comprisingdisposing a separation medium between the transport/drive belt and themat.
 14. The method as recited in claim 13, wherein the separationmedium is a separation paper.
 15. The method as recited in claim 13,wherein the separation medium includes a surface structure and whereinthe melting includes impressing the surface structure on the separationmedium.
 16. The method as recited in claim 9, wherein the mat includes aglass fiber mat.
 17. The method as recited in claim 9, wherein the matincludes a woven fabric coated with an anti-adhesive agent.